Multiple improvements to "plz watch" and "plz run".

src/run/run_step.go

@@ -2,6 +2,7 @@
 package run
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"os"
@@ -107,15 +108,26 @@ func run(ctx context.Context, state *core.BuildState, label core.BuildLabel, arg
 	// Note that we don't connect stdin. It doesn't make sense for multiple processes.
 	cmd := exec.CommandContext(ctx, splitCmd[0], args[1:]...) // args here don't include argv[0]
 	cmd.Env = env
-	if !quiet {
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-		must(cmd.Start(), args)
-		err := cmd.Wait()
-		return toExitError(err, cmd, nil)
+
+	var combinedOutput bytes.Buffer // Dump the command output here, for quiet mode.
+	if quiet {
+		cmd.Stdout, cmd.Stderr = &combinedOutput, &combinedOutput
+	} else {
+		cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
+	}
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	must(cmd.Start(), args)
+
+	if pgid, err := syscall.Getpgid(cmd.Process.Pid); err == nil && pgid > 0 {
+		go func() {
+			for range ctx.Done() {
+			}
+			syscall.Kill(-pgid, syscall.SIGKILL)
+		}()
 	}
-	out, err := cmd.CombinedOutput()
-	return toExitError(err, cmd, out)
+
+	err := cmd.Wait()
+	return toExitError(err, cmd, combinedOutput.Bytes())
 }
 
 // environ returns an appropriate environment for a command.

src/watch/watch.go

@@ -6,7 +6,10 @@ package watch
 import (
 	"context"
 	"fmt"
+	"os"
+	"os/signal"
 	"path"
+	"syscall"
 	"time"
 
 	"github.com/fsnotify/fsnotify"
@@ -39,7 +42,19 @@ func Watch(state *core.BuildState, labels core.BuildLabels, callback CallbackFun
 	files := cmap.New()
 	go startWatching(watcher, state, labels, files)
 
-	ctx, cancel := context.WithCancel(context.Background())
+	sigchan := make(chan os.Signal, 1)
+	signal.Notify(sigchan, os.Interrupt)
+	parentCtx, cancelParent := context.WithCancel(context.Background())
+	go func() {
+		for range sigchan {
+			cancelParent()
+			signal.Stop(sigchan)
+			close(sigchan)
+			syscall.Kill(syscall.Getpid(), syscall.SIGINT)
+		}
+	}()
+
+	ctx, cancel := context.WithCancel(parentCtx)
 
 	// The initial setup only builds targets, it doesn't test or run things.
 	// Do one of those now if requested.
@@ -57,7 +72,7 @@ func Watch(state *core.BuildState, labels core.BuildLabels, callback CallbackFun
 			}
 			// Kill any previous process.
 			cancel()
-			ctx, cancel = context.WithCancel(context.Background())
+			ctx, cancel = context.WithCancel(parentCtx)
 
 			// Quick debounce; poll and discard all events for the next brief period.
 		outer: